Lithornis vulturinus Owen, 1840

Bourdon, Estelle & Lindow, Bent, 2015, A redescription of Lithornis vulturinus (Aves, Palaeognathae) from the Early Eocene Fur Formation of Denmark, Zootaxa 4032 (5), pp. 493-514 : 495-496

Lithornis vulturinus Owen, 1840

1891. Proherodius oweni Lydekker, p. 363 (in part).

1977. Parvigyps praecox Harrison & Walker, p. 31 (in part). 1977. Pediorallus barbarae Harrison & Walker, p. 36.

1977. Promusophaga magnifica Harrison & Walker, p. 40.

1984. Pediorallus nasi Harrison, pp 19–21. NEW SYNONYMY 1988. Lithornis nasi (Harrison): Houde, p. 31. NEW SYNONYMY

Neotype: NHMUK A5204, partial skeleton.

Neotype locality and horizon: London Clay Formation, England; Ypresian, Early Eocene.

Referred material from the Early Eocene (Ypresian) London Clay Formation of England: NHMUK 33138, fragment of sternum and ribs embedded in a clay nodule plus proximal end of left humerus; NHMUK 38933, synsacrum; NHMUK 38934, imperfect sternum embedded in a clay nodule; NHMUK 38935, imperfect wing bones and vertebrae embedded in a clay nodule; NHMUK A225, two casts of right tarsometatarsus; NHMUK A3681, proximal part of right tarsometatarsus; NHMUK A4270, distal end of right femur; NHMUK A5278, distal end of left femur; NHMUK A5279, damaged proximal part of right tarsometatarsus; NHMUK A5195, proximal end of left tarsometatarsus; NHMUK A5197, proximal part of left tarsometatarsus; NHMUK A5198, distal part of left tibiotarsus; NHMUK A5199, distal part of left tibiotarsus; NHMUK A5200, two vertebrae thoracicae, left caput humeri, proximal end of right ulna, distal end of right femur and distal end of right tibiotarsus; NHMUK A5201, distal end of right tibiotarsus; NHMUK A5455, imperfect skeleton, dissociated elements (could not be located).

Referred material from the Early Eocene (Ypresian) Fur Formation of Denmark: MGUH 26770, articulated skeleton.

Newly referred material: NHMUK A5425, imperfect skeleton, dissociated elements, London Clay Formation, England, Ypresian, Early Eocene; NHMUK A6115, imperfect skull, damaged proximal end of right humerus and sternal fragment embedded in a clay nodule, London Clay Formation, England, Ypresian, Early Eocene; MGUH 1285, distal part of left humerus, Ølst Formation, Denmark, latest Paleocene—earliest Eocene; DK 23, subcomplete left humerus, Fur Formation, Denmark, Ypresian, Early Eocene.

Tentatively referred material. PU 23482 and UM 73103, Early Eocene Willwood Formation.

Differential diagnosis. Lithornis vulturinus differs from other species of Lithornis in the following combination of features: processus orbitalis of os lacrimale fused to os ectethmoidale only at the tip; small caudal process on os palatinum similar to that found in some tinamous; pterygoid fossa small and shallow; corpus scapulae slender and poorly curved; humerus, presence of shallow oblique groove extending from distal part of crista bicipitalis to dorsal margin of sulcus transversus; ala postacetabularis ilii only slightly sloping ventrally; crista iliaca dorsolateralis lacking marked convexity above foramen acetabuli; wide spatium ischiopubicum and large foramen obturatum.

L. vulturinus differs from L. plebius in the presence of small depression on the processus zygomaticus. L. vulturinus differs from L. celetius in the shorter processus orbitalis of os quadratum. L. vulturinus differs from L. promiscuus in the following features: smaller size; shallower fossa temporalis; smaller condylus occipitalis; lateral groove of mandibula shallow and in dorsal position.

Remarks. The holotype of Lithornis vulturinus Owen, 1840 was lost in the Second World War (Houde 1988). Consequently, Houde (1988) erected NHMUK A5204 as a neotype of L. vulturinus (see discussion below). Therefore, our comparisons are mostly based on NHMUK A5204, which is the most complete specimen available from the type formation. Aside Lithornis vulturinus Owen, 1840 , three other species are currently included in the genus Lithornis : L. celetius Houde, 1988 (Late Paleocene Fort Union and Polecat Bench Formations), L. promiscuus Houde, 1988 (Early Eocene Willwood Formation) and L. plebius Houde, 1988 (Early Eocene Willwood Formation). L. nasi (Harrison, 1984) from the Early Eocene London Clay Formation is regarded here as a junior synonym of L. vulturinus (see discussion). Another species from the Early Eocene London Clay,? Lithornis hookeri (Harrison, 1984) , is only tentatively referred to the genus Lithornis by Houde (1988).

Measurements of MGUH 26770 in mm (E, estimated measurements). Skull length (L) as preserved, 69.1; distance between foramen venae occipitalis externae and tip of processus paroccipitalis, 13.0; width (W) at medial edge of processus paroccipitalis, 10.8; L of lamina parasphenoidalis, 9.4; distance between tips of processus basipterygoidei, 10.5E; distance between tip of processus zygomaticus and tip of processus postorbitalis, 9.5; height (H) of os lacrimale (distance from tip of processus supraorbitalis to tip of processus orbitalis), 11.5; mandibula, maximum W of fossa caudalis, 7.4. Atlas: L of corpus vertebrae (cv), 2.5. Axis: L of cv (from facies articularis cranialis to facies articularis caudalis), 5.6. C3: L of cv, 4.7; W at processus transversi (prt), 6.3; C4: L of cv, 6.0; W at prt, 7.1; C5: L of cv, 7.6; W at prt, 8.0; C6: L of cv, 8.7; C7: L of cv, 9.8; W at prt, 9.5; C8: L of cv, 9.3; W at prt, 9.8; C9: L of cv, 9.6; W at prt, 9.9; C10: L of cv, 10.0; W at prt, 10.3; C11: L from zygapophysis cranialis (zcr) to zygapophysis caudalis (zca), 11.2; C12: L from zcr to zca, 10.8; C13: L from zcr to zca, 10.7; C14: L from zcr to zca, 11.0; C15: L of base of processus spinosus (psp), 2.7; L from zcr to zca, 11.0; T1: L of base of psp, 4.2; L from zcr to zca, 11.0; T2: L of base of psp, 5.6; L from zcr to zca, 11.2;T3: L of cv, 9.7; L of base of psp, 7.3; L from zcr to zca, 11.7; T4: L of cv, 10.7; L of base of psp, 7.8; L from zcr to zca, 12.3; T5: L of base of psp, 6.9; L from zcr to zca, 12.0; T6: L of cv, 10.4; L of base of psp, 6.3; L from zcr to zca, 11.8; T7: L of cv, 10.1; L of base of psp, 5.5; L from zcr to zca, 11.2; T8: L of cv, 9.8. L of base of psp, 4.5; L from zcr to zca, 10.3; Synsacrum, L as preserved, 46.4; maximal W of synsacrum, 18.5. Length of right (R) scapula, 67.0; R scapula, W of extremitas cranialis, 9.0; R coracoideum, distance from processus acrococaroideus to lateral end of facies articularis sternalis, 38.0; left (Lf) humerus, distance between extremitas distalis and proximal end of impressio musculi pectoralis, 70.1; R humerus, distance between proximal end of impressio musculi pectoralis and proximal end of caput humeri, 12.0; estimated L of humerus based on the last two measurements, 82.0; R humerus, distance between caput and distal end of crista deltopectoralis, 28.0E; R humerus, W of extremitas proximalis (from crista deltopectoralis to crista bicipitalis), 18.2; R Humerus, W from tuberculum dorsale to crista bicipitalis, 16.0E; Lf humerus, L of crista deltopectoralis, 24.0E; Lf humerus, W of shaft at distal end of crista deltopectoralis, 6.3; Lf humerus, W of shaft at mid-H, 5.5; Lf humerus, distance between extremitas distalis and distal end of crista deltopectoralis, 52.0; L of Lf ulna, 72.6; L of Lf radius, 67.1; Lf os carpi ulnare, H of ramus dorsalis, 5.3; L of Lf carpometacarpus, 40.0; L of Lf phalanx digiti alulae, 20.0; L of Lf phalanx proximalis digiti majoris, 16.0; L of Lf phalanx distalis digiti majoris, 18.0; L of Lf phalanx digiti minoris, 8.1; ilium, L from cranial end of ala preacetabularis ilii to caudal edge of antitrochanter, 35.9; distance between tip of tuberculum preacetabulare and crista iliaca dorsalis, 12.5; distance between tip of tuberculum preacetabulare and caudal edge of antitrochanter, 10.5; H of foramen acetabuli, 6.5.